TEM(thin specimen) SEM (usual specimen) ---------Electron gun ---------Electron gun ◆-====”-First aperture ---"First condenser lens --Condenser lens 4-------Second aperture 4-----Second condenser lens ◆===st aperture CRT Specimen ..-.Third aperture ---Objective lens ---Scanning coil Second aperture Intermediate lens ----Final condenser lens -Final aperture ---Projection lens Shower of electrons Signal for electronic 。------Final aperture Specimen image formation on CRT Electron collector ....-Final image TRANSMISSION SCANNING ELECTRON MICROSCOPE ELECTRON MICROSCOPE Figure 4.13:Ray diagram of a transmission electron microscope and a scanning electron microscope 77 TEM (thin specimen) SEM (usual specimen)